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From Alexander Paschenko <alexander.a.pasche...@gmail.com>
Subject DML data streaming
Date Wed, 08 Feb 2017 15:00:23 GMT
Hello Igniters,

I'd like to raise few questions regarding data streaming via DML statements.

Currently, all types of DML statements are supported (INSERT, UPDATE,
DELETE, MERGE).

UPDATE and DELETE are supported in streaming mode only when their
WHERE condition is bounded with _key and/or _val columns, and UPDATE
works only for _val column directly.

Seeing some activity in direction of hiding _key and _val from the
user as far as possible, these features seem pointless and should not
be released, what do you think?

Also INSERT in streaming mode currently does not throw errors on
duplicate keys and silently ignores such new records (as long as it's
faster than it would work if we'd introduced receiver that would throw
exceptions) - this can be fixed with additional flag that could
_optionally_ make INSERT slower but more accurate in semantic.

And MERGE in streaming mode currently not totally accurate in
semantic, too - on key presence, it will just replace whole value with
new one thus potentially making values of some concrete columns/fields
lost - this is analogous to
https://issues.apache.org/jira/browse/IGNITE-4489, but hardly can be
fixed as long as probably it would hit performance and would be
unresonably complex to implement.

I suggest that we drop all except INSERT and introduce optional flag
for its totally correct semantic behavior as described above.

- Alex

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